1. Field of the Invention
The present invention relates to the construction of single-hung and double-hung windows. More particularly, the present invention relates to windows having components mounted on a window sash for preventing a window sash from cocking or wobbling in the window frame.
2. Prior Art Description
There are many types of windows used in modern construction. Some windows are designed to open, some are not. Of the windows that are designed to open, some windows have sashes that open vertically and others have sashes that slide open laterally, or rotate outwardly.
Windows that have vertically opening sashes are the most common window used in residential home construction. Vertically opening windows are either single-hung, having one sash that opens, or double-hung, having two sashes that open. In both single-hung and double-hung windows, a counterbalance system is used to hold a window sash up once it is opened. If no counterbalance system is used, gravity causes the sash of the window to close as soon as it is opened and released.
Counterbalance systems for single-hung and double-hung windows typically use coil springs to counterbalance the weight of the window sashes. The presence of a counterbalance system requires that a substantial space be left between the sash of the window and the jambs of the window frame. The counterbalance system operates in this space. The counterbalance system is protected from view and from contact by using extruded window frame jambs that are generally U-shaped in cross section. The counterbalance system sits within the center of the groove defined by this track and is thus protected from sight.
When a window is manufactured, the sashes of the window are made separately from the frame of the window. The sashes are later assembled into the frame.
Due to variations in manufacturing tolerances, the length of a window sash may vary by up to ⅛th of an inch. Likewise, the distance between jambs in a window frame may also vary by up to ⅛th of an inch. As a consequence, if an undersized sash is assembled into an oversized window frame, there may be over ¼ inch of play between the sash and the tracks of the window frame.
If a window sash has too much play in a window frame, the window sash may cock in position when moved by a person or when influenced by the counterbalance system. Additionally, if the window sash cocks in position, a gap may be created between the window and the sill, thereby greatly reducing the insulation rating for that window.
A need therefore exists for a system that can be added in a window assembly, both at its time of manufacture and retroactively, that prevents the window sash from cocking. This need is met by the present invention as described and claimed below.